1. Field of the Invention
The present invention relates to a technology for mounting a chip on a resin film, more particularly to a technology for fixing a chip to a resin film by discharging a certain amount of adhesive.
2. Background Art
In recent years, a technology that involves a bare chip made of a semiconductor mounted on a wiring board has been developed, and the technology has been frequently used to manufacture miniature electronic devices such as mobile phones since a packaging area can be made smaller than that of a case where a chip molded into a resin is mounted.
FIGS. 7 (a) to (e) describe a conventional process for mounting a bare chip. First, referring to FIG. 7 (a), numeral 113 shows a base film composed of a flexible resin and a wiring film 122 composed of a patterned copper foil formed on the surface of the base film 113.
To the surface of the base film 113 on which the wiring film 122 is formed, an anisotropic conductive film 115 is affixed as shown in FIG. 7 (b). The base film 113 is placed on a preheating table 151 while orienting the back side thereof downward as shown in FIG. 7 (c).
The anisotropic conductive film 115 is composed of a thermosetting resin as a main agent and conductive particles are dispersed in the main agent.
The preheating table 151 is preheated at a temperature higher than the curing temperature of the main agent contained in the anisotropic conductive film 115. Thus, the anisotropic conductive film 115 is heated by heat transmitted through the base film 113.
The main agent of the anisotropic conductive film 115 is semi-hardened by placing both the base film 113 and the anisotropic conductive film 115 on the surface of the base film 113 on the preheating table 151 for a predetermined time.
Next, as shown in FIG. 7 (d), the base film 113 and the semi-hardened anisotropic conductive film 115 are moved from the preheating table 151 to a working table 152; a semiconductor chip 111 is retained by a pressing jig 129; the semiconductor chip 111 is moved to a position above the anisotropic conductive film 115; a bump 121 of the semiconductor chip 111 and a connecting part of a wiring film 122 are so positioned as to face each other; and then, as shown in FIG. 7 (e) when the semiconductor chip 111 is pressed against the anisotropic conductive film 115 by the pressing jig 129, the bump 121 digs into the anisotropic conductive film 115; thereby the bump 121 is connected electrically to the wiring film 122 through conductive particles dispersed in the anisotropic conductive film 115.
Since the pressing jig 129 and the working table 152 are heated at a temperature higher than that of the preheating table 151, by keeping the jig 129 to be pressed against the back side of the semiconductor chip 111 for a predetermined time, the main agent in the anisotropic conductive film 115 hardens and, thus, the semiconductor chip 111 is fixed to the base film 113.
In the case where the anisotropic conductive film 115 is hardened as above, the anisotropic conductive film 115 is first heated on the preheating table 151, the film is moved to the surface of the working table 152 after the film is semi-hardened, and then mounting and heating of the semiconductor chip 111 is performed; thereby heating time on the working table can be shortened by the extent corresponding to the previous semi-hardening.
However, if the semiconductor chip 111 is mounted on the anisotropic conductive film 115 on the working table 152 and the progress of the process is suspended, under the process of preheating before the mounting since the anisotropic conductive film 115 is also kept on the preheating table 151 for a long time, both of the anisotropic conductive films 115 become defective.
An alternative processing technique involves using a liquid adhesive material applied onto the base film 113 in place of the anisotropic conductive film 115. However, this processing has the problems that the material is likely to immix bubbles as compared with the anisotropic conductive film 115. As a result, a defect in aging caused by voids frequently occurs.